[unreadable] A Research Career Award (K02) would support 5 years of programmatic research into young children's family relationships and early social and emotional development. The applicant's prior experience and expertise in family relationships and complex family systems places the applicant in a unique position for studying the changes that occur in family life and children's adjustment during the transition period following the birth of a baby sibling. Few studies have examined this important developmental period in the young child's life and this will be the first large-scale study designed to investigate the complex interrelations of change trajectories in individual development and family relationships across the transition to siblinghood. The institutional environment is strongly supportive of the research program and extensive resources are currently in place. The applicant's recently funded NICHD study, "Family Transitions following the Birth of a Sibling" will be the primary focus of the award period. In this study 200 families are followed longitudinally beginning in the prenatal period and then at 1, 4, 8, and 12 months after the sibling's birth in order to examine changes in family relationships (e.g., marital, parent-child), the older sibling's adjustment to the arrival of a baby sibling, the development of secure infant-parent attachments, and the early origins of the sibling relationship. One of the primary aims of this work is to identify different change trajectories over time in individual and family functioning and to examine personal characteristics of the parents, the children, and contextual characteristics (e.g., work, social support, marital) as prenatal predictors of different change trajectories. One of the major strengths of this study is the inclusion of fathers in every aspect of the research program. Several different directions have been outlined with respect to the applicant's learning and professional growth, including an understanding of (1) the biological processes underlying depression, social relationships, and emotional expression; (2) theory of mind development and its relation with sibling relationships; (3) gender differences in adult depression, and (4) the emergence of early self regulation in toddlerhood. The candidate will also acquire advanced training in statistical analyses for multivariate longitudinal data including hierarchical linear modeling. The ultimate goal of this Award is to develop a programmatic line of research on young children's socioemotional development in the context of changing family relationships that will eventually contribute to an understanding of how the interplay between biology and complex family systems affects children's social and emotional development in the infant, toddler, and preschool years. Findings from this research will inform future prevention and intervention efforts by identifying the various ways older children adjust to the arrival of a baby sibling, the biological and social factors that predict different patterns of adjustment over time, and the consequences these changes have for children and family functioning in subsequent years. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]